This invention relates to liquid level control arts, and more particularly, to apparatus for maintaining the water level in a swimming pool or the like within predetermined maximum and minimum levels.
The water level within a swimming pool should be kept within a rather narrow range in order that the skimming portion of the recirculating and filter apparatus will function properly. This level is usually maintained by simply observing the water level and supplying makeup water from a line source with a manually operated valve. However, because the volume of water necessary to make up even a slightly lower level is considerable, the time necessary to bring the water to the desired level may be several hours, a circumstance which renders the task unpleasant and additionally, brings about the possibility of overfilling due to failure to monitor the progress of the operation carefully enough. Thus, it will be apparent that it would be highly advantageous to provide automatic means for maintaining the water level of swimming pools or like liquid reservoirs within predetermined maximum and minimum levels without the need for manual supervision or intervention which includes a fail safe back up system incorporated therein to prevent overfill if the automatic system fails while in the fill mode.
There are numerous automatic fill systems in the art directed to fill control of swimming pools and the like. These systems generally utilize float valve means to control the flow of new or additional water into the reservoir. These systems employ either mechanical or electrical valve control means responsive to float vertical positions. Although most of the prior art devices use a single liquid input control valve associated with a float, some prior art devices include a reservoir within valve means separating input and output conduits and includes a float actuated valve in both the input and output conduits whereby a single leaking valve will not cause overfilling of the swimming pool or reservoir.
U.S. Pat. No. 2,068,138 teaches a two stage float actuated valve system utilizing a pair of internal reservoirs each with a float and valve for controlling the flow of liquid into the reservoirs. One float and valve combination is the primary liquid flow control valve and the second acts as a backup in the event the primary valve fails to close off liquid flow into the reservoirs. Both valves are actuatable between open and closed states.
Obviously, in all the above prior art automatic fill valves a failure of one or both of the float valves will result in an overfill of the swimming pool or the like liquid reservoir.
Although some of the prior art devices are moderately successful in operation, none of the devices provide a fail safe lock on means for terminating the flow of liquid into a reservoir in the event of valving failure while in the fill mode.